We explain what the lithosphere is, its layers and why it is so important. In addition, the continental lithosphere and the oceanic lithosphere.
What is the lithosphere?
The lithosphere or lithosphere is the most solid and superficial layer of planet Earth , that is, the most rigid and external of all. It communicates the surface on which we humans live with the asthenosphere, the next layer in depth. It is usually considered as the union of the earth’s crust with the top layer of the mantle.
The name of the lithosphere comes from the Greek words lithos (“stone”) and sphaíra (“sphere”). This layer varies in average thickness. It is not simple to determine exactly where it begins and where it ends, and that is why we can talk about two types of lithosphere, which are:
- Continental lithosphere , made up of the continental crust (that is, the continents ) and the outermost region of the earth’s mantle, mostly composed of granite-type stones, and reaches about 120 km thick.
- Oceanic lithosphere , which is the portion of the earth’s crust that makes up the ocean floor , is much thinner than the continental (just 65 km thick) and is mostly made up of basaltic rocks.
On the other hand, the lithosphere is fragmented into different blocks known as tectonic plates or lithospheric plates, on which the earth’s crust is. These plates can move at a rate of a few centimeters a year.
Their movement is due to the fact that they are on the most viscous materials that make up the earth’s mantle. Frictions are caused to each other, which we know as earthquakes. To this same phenomenon we owe the orogenesis ( mountain formation and geographical accidents) and magmatism or volcanism.
Layers of the lithosphere
The lithosphere is composed of two layers, essentially, which are:
- The earth’s crust . The outermost solid region of the globe, on which human beings and other known living beings come to life . As we have seen before, it can be of two types, depending on whether it is part of the continents (continental crust, of greater thickness) or of the seabed (oceanic crust, of less thickness).
- The upper region of the earth’s mantle . The earth’s mantle is the most abundant inner layer of the planet (84% of it), composed of silicated materials and extending from the end of the earth’s crust to the outer part of the planet’s core (about 2900 km deep). It is divided into upper mantle and lower mantle, with the upper region of the first one being part of the lithosphere. It is a very dense and viscous layer, on which tectonic layers can move.
Importance of the lithosphere
On the one hand, the lithosphere is important because it contains the earth’s crust, on which we live. On the other hand, their movements modify our way of existing , such as seismic activity (tremors, earthquakes , seismic failures), magmatic activity (volcanoes) or even the very formation of mountains (orogenesis).
Let us also think that the only terrestrial layer that we have really been able to study directly is the lithosphere, so it is the one we know best. The others we know from measurements, experiments and scientific deductions, since they are too deep to dig.